1. Field of the Invention
The apparatus of the present invention relates to sealing the annulus between an internal carrier pipe and an external casing. More particularly, the apparatus of the present invention relates to a device for securing the two ends of a section of casing around an internal carrier pipe to provide a fluid seal within the annular space between a carrier pipe and a casing particularly suitable for underground crossings of pipelines.
2. General Background
In the construction of underground pipelines which are utilized for carrying natural gas or the like materials underground, a special consideration is given to safety in those sections of the pipeline that cross beneath public thorough fares such as highways or railroad crossings. In compliance with present regulations for these safety considerations, it necessary that the underground pipeline which carrying the natural gas be covered with a length of protective housing such as a casing along the entire length of the pipeline substantially the width of the public thoroughfare for the public safety. Following the placement of the carrier pipeline in the casing, the ends of the casing must be sealed off so that ground water or other extraneous materials cannot enter the annulus and also allow the filling of this annulus with a highly viscous fluid to eliminate corrosion of the carrier pipeline and therefore would prevent leaks from inadvertently occurring under ground which may of course result in a hazardous condition in the area of public thoroughfare.
In addition, in the event a section of pipeline should become corroded or the like, it may be necessary to remove that portion of the pipeline beneath the section of the thoroughfare, and therefore the outer casing must be replaced and resealed against the new section of pipeline.
One of the problems that is confronted in the placement of the protective casing around the inner carrier pipe is a problem of assuring that there is a fluid tight seal between the casing and the pipe. There have been various attempts to perfect this seal, and in the present state of the art all these attempts have fallen short. Particularly in the area when the pipeline must be replaced as opposed to the new construction. One of the more serious problems confronted is the fact that the carrier pipe is very often not centered and is not co-axially aligned with the external casing. Therefore, if one were to attempt to place a "rubber boot" for example in the annulus between the pipeline and the casing in order to affect a seal, in view of the fact that the annulus is asymmetrical, it would be virtually impossible to create a proper seal continuously between all sides of the internal pipe and the internal surface of the casing. Therefore, there is much added expense, effort and safety hazards in order to finally achieve the results.
The apparatus of the present invention, in the preferred embodiment, would overcome all of the problems that have been confronted in the sealing of the casing and the internal carrier pipe, both in new construction and in the replacement of a section of pipeline.
Several patents have issued in regard to the sealing of pipes, the most pertinent being as follows:
______________________________________ INVENTOR: PATENT NO. ISSUED: ______________________________________ A. J. Avery 603,720 May 10, 1898 H. Moeser 317,408 May 5, 1885 J. A. McCormick 329,405 October 27, 1885 J. A. McCormick RE 10,674 December 15, 1885 G. Westinghouse, Jr. 400,532 April 2, 1889 J. A. McCormick 335,467 February 2, 1886 R. L. Hasche 2,196,766 April 9, 1940 O. B. Evans 220,064 September 30, 1879 Roger F. Wells 4,452,277 June 5, 1984 ______________________________________